Color node losing shade
Most likely you have accidentally put the HSV node to a value that blows out the resulting pixel values. See this screenshot here to understand which value I mean:



In your case, you have set this to 2.0. This will likely send so much light energy down the line that the resulting pixels will overshoot the 1.0 range, thus being clipped to white. I've done this in the screenshot below:



Lower that input value of the HSV node to something reasonable (between 0.0 and 1.0) and see if this resolves the issue.